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Can you see my heart beating? A snake with a very big problem!

I received an unusual phone call recently from the owner of an 18 month old False Water Cobra (Hydrodynastes gigas), a South American rear-fanged, mildly venomous species of snake (http://www.reptilesmagazine.com/Snake-Species/False-Water-Cobra/). The owner had noticed shortly after acquiring the snake that it had what was described as a wound on it’s underside through which you could see it’s insides! Naturally, I was quite worried so asked for the snake to be brought in for examination, and in the meantime they emailed me some photos and reassurance that the snake was acting perfectly normally, eating and defaecating fine and didn’t seem in any way bothered by the strange ‘wound’.

Having examined the animal, it appeared that she had a defect in the body wall on her ventral surface or belly with a large hole visible in the ventral muscles. Bizarrely, this defect was at the level of the heart about a third of her length down her body. The only tissue separating her visibly beating heart from the outside world was a thin membranous layer of body cavity lining and some connective tissue which was quite transparent. I have seen some similar lesions in reptiles at the umbilicus or site where the blood vessels carry nutrients into the growing embryo from the egg or from maternal tissues in the case of live bearing species. Sometimes when these animals hatch or are born the hole in the body wall fails to close completely and an umbilical hernia or body wall defect is left behind. However, I have never seen or even heard of such a defect high up on the body overlying the heart! I concluded that this must be a congenital problem that the snake was born with, perhaps a fluke genetic mutation or a developmental insult during incubation of the egg which disrupted the normal growth of the embryo resulting in a physical abnormality at birth. Having spoken to a few reptile enthusiasts in the UK who keep this species of snake, it turns out there have been a few reported with the exact same defect in the exact same place, so it looks likely this is a genetic problem, most likely caused by inbreeding in certain lines due to relatively low genetic diversity in the UK population.

The risk of leaving the snake in this condition was that during the course of her life she may snag this fragile membrane protecting her heart and eviscerate herself or worse still puncture her heart. Although this risk was small, it would be safer to carry out a surgery now than always wonder and worry if she might do some damage and seriously injure herself, when pulling off her shed skin for example. I admitted her and set her up in our reptile ward in a heated vivarium to bring her body temperature up to preferred range. Once her temperature was correct I injected her with a combination of sedative drugs into the muscle in her back. I say I injected her, but actually I restrained her with a thick pair of gloves whilst my nurse Justyna gave her the injection. She was very feisty, strong, and objected to restraint, trying to bite the gloves. Obviously considering her potential to give a painful bite and possible envenomation we took great care at this stage. Rear fanged snakes are different to other venomous species in that they have modified salivary glands and teeth at the back of their mouth, with which they chew their prey in order to inject and subdue it. Therefore it would be difficult to get a dangerous bite from a rear fanged species unless you allowed the snake to chew on you. Front fanged species can deliver a dry or wet bite from the front of the mouth with a rapid strike and minimal contact so are far more dangerous to work with and handle. After her injection we left her back in her hospital vivarium in the correct temperature to allow her to metabolise the drugs efficiently. Ectothermic or ‘cold-blooded’ animals such as reptiles rely on external temperature to control their biological functions and metabolic rate, so it is vital when treating ill specimens and indeed when undertaking anaesthesia and surgery to maintain their body temperature in the correct range so everything runs smoothly and drug dosages work effectively. After about a 20-30 minute induction period, now nice and relaxed after her sedation we removed her and placed her into an anaesthetic gas chamber so she fell further asleep and we could position and prepare her for surgery. She was maintained under anaesthesia by using a gas mask delivering a safe gaseous drug called Sevoflurane. Normally for a prolonged surgical procedure in a snake I would intubate the animal with a solid plastic or rubber tube placed into the windpipe or trachea for better control and access to her airway should she stop breathing for instance, but in the case of venomous species I prefer not to mess around in the mouth due to the risk of accidental envenomation. A correct sized mask with her head taped inside in place and sealing the entrance provides the next best option and is safer for all involved.

Once Justyna prepped her with a surgical scrub and insulating layers to maintain her body temperature lying belly up on a surgical heat mat, I was ready to begin. I carefully dissected away the thin membrane covering her heart from the scales on either side of the deficit. I had to be extremely careful as this layer of tissue was so thin and the heart was literally beating against it directly underneath. Tiny blades and scissors were required, and I cut in time between the beats to avoid cutting at the moment the heart filled to maximum capacity with blood. Myself, Justyna and the veterinary student who is seeing practice with us this week to learn more about exotic pet medicine were all holding our breaths at times. Credit to the student Conor for taking the photographs while I operated by the way. Justyna found this anaesthetic very easy to monitor throughout as we were literally watching the heart beating throughout so she could record heart rate and strength with the naked eye for a change! Often we use sensitive probes to monitor heart rate through the body wall but not needed in this case.

And here is a video during the surgery when I had carefully dissected away the thin tissue revealing the heart beating underneath before I began to suture the defect closed:

Once the tissue had been separated away from the half sized scales lining either side of the lesion I set about suturing the hole back together, bringing the soft tissue of the internal body wall and the edges of the scales together to meet in the middle and form a tight seal which would heal and protect the heart and blood vessels underneath. I was quite happy with a neat and tidy job at the end. She was given a long acting pain medication and anti-inflammatory by injection, and a reversal drug for the sedatives given earlier and placed back in a clean dry cage with paper substrate to recover. We turned up the heat temporarily to boost her metabolic rate and aid her clearance of the anaesthetic drugs, and within 20 minutes she was groggy but wandering around her cage getting her bearings again. It always surprises me how tough these animals are. Reptiles have been around for millions of years and they really are quite resilient and remarkable in what they can withstand. Many of my clients fret and worry about anaesthetic risk in particular if their pet reptile needs a surgery for example. Although the general risk is higher than in dogs and cats I find them to be remarkably sturdy anaesthetic patients for the most part, so the risk is still quite low as long as you seek out an experienced and knowledgeable reptile vet.

In terms of aftercare, she just needs to be kept clean and dry. No antibiotics were prescribed as it was a sterile op and good hygiene practices should prevent infection from here. Being a semi-aquatic species that likes to bathe in water, I’ve specified that she is not allowed a water dish in which she could submerge as the wound could act as an entry point for water and bacteria or other contamination into the body cavity if she submerged in the coming week or so. I will keep her in overnight and send her home tomorrow. So far she is making an excellent recovery. The sutures I placed are dissolvable over time and should slough off the next time she sheds her skin or possibly after that, so I just need to recheck her in a week to make sure the wound looks good, is healing well and is free of infection. Problem solved!